The present invention relates generally to imageable media. More particularly, the present invention relates to image retaining media for such things as identification cards.
A laminate in accordance with the present invention may be utilized for such things as identification cards. Identification cards and related products have been used for many years as a means for persons to establish their identity and credentials. These identification cards may include a number of images.
One popular method of imaging identification cards has been through the use of a printing process known as diffusion dye thermal transfer (D2T2). In this printing process, heat is utilized to cause a colored dye to migrate into a layer of the card construction. This process in described in commonly assigned U.S. Pat. No. 5,688,738 entitled Security Card and Method for Making Same. Despite its obvious utility, the D2T2 imaging process is a relatively expensive one, both in the cost associated with the equipment to perform this process, and the cost associated in the required printing ribbons. When a particular organization produces a large number of cards, there is a large incentive to keep the cost of each card low.
With the advent of low cost, high quality inkjet printers, there has been a great deal of interest in ink-jet printing security cards. Inkjet techniques have become vastly popular in commercial and consumer applications. The ability to use a personal computer and desktop printer to print a color image on paper or other receptor media includes both dye-based and pigment-based inks. The latter provide more durable images because pigment particles are contained in a dispersion before being dispensed using a thermal or piezo inkjet print head from inkjet printers.
Typically, pigment based ink systems have found use in wide-format inkjet printers for outdoor or back lighted sign applications. The extra durability of the pigments is required to prevent fading from extended exposure to UV light. Because of the typical size of the imaged graphic and intended viewing distance of the graphic, the resolution of the graphic need not be a photo realistic rendition. In addition, the wide format graphics need good color saturation, which can be provided by higher ink delivery volumes. Typical wide format printers have resolutions from about 180 to 600 drops per inch (dpi) and dispense 30 to 140 picoliters of ink per drop.
The desk top inkjet printers have diverged from the wide format printers because of the intended use. Photo images now can be digitally made and stored on magnetic media, optical disks, or computer memory. There is demand to be able to print photo realistic graphics at home or office quickly and economically. Because of simplicity of operation, economy of inkjet printers, and improvements in ink technology, the inkjet imaging process is satisfying that demand. To get the continuous tone appearance required for photo realistic graphics, some inkjet printer manufacturers have offered printers that have higher resolution, smaller drop volumes, and additional colors. Now, a typical desk top inkjet printer can have resolution to 1440 dpi and drop volumes as low as 3 picoliters. In addition, some inkjet printers jet more than the standard cyan, yellow, magenta, and black (CYMK) colors. Additional colors such as light cyan and light magenta have been added to increase the effective resolution by changing the dithering patterns formerly required. These types of improvements to inkjet printers have lowered the total amount of required ink used and closed the image quality gap, enabling images produced by inkjet printers to now be capable of competing with images made by thermal dye transfer printing technology. Also, a nice feature of aqueous inkjet printers is that the printers can work in home and office environments, whereas the solvent based inkjet systems with emissions cannot.
The water present in aqueous ink solutions is a source of various technical difficulties. Aqueous solutions are slow to dry, sensitive to humidity, and susceptible to deterioration by water soaking. Excess water can cause image distortion and bleeding of the image. When an image is printed on a card substrate, excess water can reduce or prevent bonding between the layers of the card, which in turn can lead to problems with delamination and/or tampering. Excess water may also cause bubbling of the card during lamination.
Suitable receptor media has not existed for the security card industry for inkjet printing because of the high application demands placed on the card. Current inkjet media usually contains water swellable coatings, binders, or absorbing pigments, such as all forms of silica, alumina, zeolites, methylcellulose, polyvinyl alcohol, and the like. If particles such as zeolite particles are used, the particles are usually bound together in a system that is binder deficient. If too much binder is used, no inter particle porosity would be obtained. If not enough binder is used, the particles could fluff off like powder from the printing surface. Great care is given to the binder to particle ratios in order to reap benefits of porous media and, until now, this has been one of the only practical ways to achieve an ink-jet printable surface. These particles are needed because the inkjet ink itself can be aqueous. Media with these types of materials can be inherently slow to dry, are sensitive to humidity, prone to delaminating in the layer containing a high concentration of particles and delaminating and damage from external water soaking. Hence, the current commercially available paper or film coating technologies do not work for ID cards and have not been made available for that application. Furthermore, the current inkjet receptor media is not sufficiently durable to withstand scratching and the wear and tear placed on a ID card. To prevent this wear and tear, the graphic printed on the current media may be laminated with a protective plastic layer that is coated with pressure sensitive adhesives. Some inkjet receptor media coating have been made to be used without a laminate to withstand wear and tear, however, they tend to be too brittle for flexible cards. These coatings may also not be waterproof enough to prevent ink transfer. Laminates with hot melt adhesives exist and can be applied to inkjet generated images but must be laminated after the image is completely dry, to eliminate gas bubbles from the water and other volatile ink components upon heating. Also, the current media does not have the look and feel of credit cards that consumers are used to and, therefore, the current media would have to be attached to a stiffer substrate adding more potential delamination.
Japanese Patent No. 11129685A discloses an ID card and methods to print ID cards without ink to the edges in order to avoid the problem of the inkjet ink causing delaminating problems. However, many card issuers have applications where they want the aesthetics of edge to edge printing.
U.S. Pat. No. 5,928,789 discloses the need to essentially glue the ink receptive layer to a substrate again underscoring the difficulties in permanently attaching an inkjet receptive surface.
U.S. Pat. No. 5,443,727 discloses materials and a method for printing on a porous media and subsequently fusing the pores shut thereby encapsulating the image This art requires the porous film to be laminated to a substrate for support because it is not formed as an integral part of the substrate.
U.S. Pat. No. 4,384,047 discloses a process for membrane formation using vinylidene fluoride polymer. This patent teaches the need to control the casting solution temperature and humidity above the coating knife and subsequent washing steps to create a wrinkle free film which is in sharp contrast to the simplicity of the current invention""s process.
U.S. Pat. No. 4,496,629 discloses a coating layer that can be described as micro-cracks which contain zeolites or synthetic zeolites and other inorganic particles. The ratio of binder to particles is 1:20 to 1:5.
U.S. Pat. No. 3,615,024 teaches how to make skinned membranes. They use harsh solvents and low solid concentrations in the coating solution when using polyvinyl chloride. Also a water wash step is required.
U.S. Pat. No. 4,048,271 discloses a Dry Process for solvent phase inversion membranes. The disclosure of this patent underscores the need for higher molecular weight polymers for phase inversion for free standing films, whereas the integral casting on a substrate of this invention allows the use of lower molecular weight polymers.
European Patent Application No. EP 0 904 953 A1 uses a system of bonding PVC particles to one another to form porosity.
U.S. Pat. No. 5,374,475 discloses the need of perpendicular pores formed out of colloidal suspensions or the use of a nonporous layer underneath the pores to absorb ink in order to be an effective ink receptor. The art also does not permit the use of particles or filler materials.
An imageable media is disclosed. An imageable media in accordance with the present invention comprises a substrate having a first surface and a porous layer overlaying the first surface of the substrate. In a useful embodiment, a plurality of particles are disposed within the porous layer. It should be noted that in another preferred embodiment, there is no particular order or arrangement to the particles. In another preferred embodiment, a plurality of zeolite particles are disposed within the porous layer. In a particularly preferred embodiment a plurality of zeolite particles and a plurality of cross-linked polyvinylpyrrolidone particles are disposed within the porous layer.
An imageable media in accordance with the present invention may be utilized to fabricate identification cards, driver""s licenses, passports, and the like. In a preferred embodiment, the image receptive material is adapted to receive an image comprised of aqueous ink. In a particularly preferred embodiment, the image receptive material is adapted to receive an image comprised of aqueous pigmented ink adapted for use in an inkjet printer. A printed image in accordance with the present invention preferably includes one or more security indicia. Examples of security indicia that may be suitable in some applications include a picture of a human face, a representation of a human finger print, barcodes, and/or a representation of a cardholder""s signature.
The imageable media printed with dye ink is rendered tamper, water and scuff resistant, by hot fusion with a laminate. In a preferred embodiment the imageable media printed with pigmented ink is rendered tamper and scuff resistant, waterproof, and outdoor durable by simple heat sealing without adhesives, hot melts, coatings, or laminates.